It is well known to provide a sieve or sieves in the grain cleaning system of an agricultural combine. Typically, the cleaning system will consist of two sieves, an upper or coarser sieve or chaffer located below the threshing mechanism or separator of the combine and having larger sieve openings for the passage of grain and smaller pieces of plant material therethrough but relatively little of the larger chaff, and a lower finer sieve located below the chaffer for receiving the grain and smaller pieces of plant material therefrom and having smaller sieve openings for passage of the grain therethrough but relatively little of the plant material. The collected and cleaned grain, once through the sieves is then typically transported by conveyor or other means to a clean grain tank or bin on the combine, or to an accompanying grain receiving vehicle. The opening sizes of the chaffer and sieve are important parameters for controlling the amount or yield of grain that is recovered by the combine as opposed to discharged therefrom with the chaff and other unwanted plant material and crop residue. Accordingly, the chaffer and sieve opening sizes are typically set at the commencement of the harvesting operation, and may be reset at times during the harvesting operation, to achieve a desired crop yield rate.
A typical sieve construction includes a plurality of elongate parallel, pivotally mounted slats, each slat including a plurality of longitudinally spaced upwardly extending inclined fingers, the slats being pivotable through a range of open positions angularly oriented to horizontal for providing a corresponding range of openings or spaces between the fingers of adjacent ones of the slats. A typical sieve includes an adjusting member which contacts each of the slats, and a linkage and/or cable arrangement connected between the adjusting member and one or more manually or automatically movable adjusting elements or adjustors, in the latter instance, which can be moved by an actuator driven by an electrical, fluid, or other controller for moving the linkage or cable arrangement and member and thus changing the angular orientation of the slats and as a result, the opening size. The typical controller includes at least one processor operated by stored commands and/or inputs for controlling an electrical drive motor or the like for moving the actuator. An input device such as a push button or keypad and a display device are typically located in the operator cab of the combine for changing and showing the chaffer and sieve settings.
As combines have increased in capacity, the sieves have grown in size. Sieves are also typically removable for cleaning, service, and the like. Because of the larger size of the sieves, it is desirable for them to be divided into separately removable segments, for instance, a front segment and a rear segment, or a plurality of segments arranged in end to end order. And, because of the larger size, and other factors, such as uneven wear, it can be difficult to evenly adjust a sieve evenly across the extent thereof. Or, it may be desirable to adjust the segments differently, to achieve a desired cleaning effect. For instance, it may be desirable to set the opening size of the more frontward segments or segments at a more closed setting and the more rearward segment or segments more open, as towards the front end of the sieve there is typically more loose grain present, and toward the rear end there is typically more material other than grain such as larger pod or cob fragments, and the like.
As a result, what is sought is an adjusting mechanism for a sieve which does not increase the overall size or operating envelope of the sieve. It is also sought to provide a sieve which allows separate or joint adjustment of adjacent sieves or sieve segments, and also sieves of different types. Still further, the adjusting mechanism should allow for the removal of the sieves, and should be durable and long lasting.